[Coral-List] [EXTERNAL] Re: effect of sunscreen on corals

Avigdor Abelson avigdor at tauex.tau.ac.il
Sat Feb 9 02:55:49 UTC 2019

The issue of using toxic sunscreens is much simpler than one is trying to make out of it. These products should be banned, as some decision-makers wisely decided to do, and global warming has nothing to do with it.
1. There is more info than the article in ‘The Conversation’ is presenting (as Mike Risk has tried to explain, and the reply tried to take him to climate change, which is a different story all together). The information we have so far is enough to make us cautious about the use of toxic sunscreens.
2. There are non-toxic sunscreen alternatives. So the “conflict” of public health versus the protection of the reef simply doesn’t exist (as opposed to the notion raised in ‘The Conversation’ article)
3. The little we know about the toxic effects of the commonly-used sunscreens seems to be enough to ban their use, both for the environment and human health. Ecologists and environmental scientists should avoid defending human actions, the safe use of which is questioned. We can’t overlook a key principle environmental scientists should adopt (“the precautionary principle”; Kriebel et al. in Environ Health Perspect. 2001)  when dealing with or advising policy-makers.  The precautionary principle has four central components, of which, two are worth noting in related to the sunscreen issue: first, “taking preventive action in the face of uncertainty”. Again, the current information we have is enough to support a precautionary approach, that is banning the use of toxic sunscreens.  The second component, “exploring a wide range of alternatives to possibly harmful actions”, is already here. As mentioned, there are already substitutes of the toxic sunscreen products, which are less harmful, so no conflict between human health and the environment health, and therefore, no reason to encourage the continuing use of the toxic products.
I can’t understand why ‘global warming’ got into this issue. We have to fight ‘climate change’, as there are no other threats, and we have to fight local stressors as there are no other threats - dealing with one stressor should not affect our fights against the others.

On 8 Feb 2019, at 1:25, Bargar, Timothy via Coral-List <coral-list at coral.aoml.noaa.gov<mailto:coral-list at coral.aoml.noaa.gov>> wrote:

I was asked several years ago to help biologists at the USVI National Park
understand whether or not they should be concerned about sunscreen
chemicals.  There were some articles showing adverse effects in aquatic
organisms that had been exposed to the active ingredients in sunscreen
lotions, so their concern was understandable.  But like I said before, the
dose makes the poison.  If you elevate exposure enough, you could see an

I suggested to them that coastal waters at some of their high and low use
beaches be sampled to determine what active ingredient concentrations were
present.  My thought process was 2-fold.  First, the ocean is terrific at
dilution because of the tremendous water volume available.  There is a
cliche in aquatic toxicology, "dilution is the solution to pollution".  I
was not expecting to see very high concentrations, but we don't know that
without investigating.  Second, if we sampled at some of the high-use
beaches and still didn't see much, then the likelihood of effect (i.e.
risk) would be very low there, and certainly so where visitation was low or
essentially non-existent.  So we went out and collected samples, largely
within 5-10 m of the surf zone.  Most of the samples had concentrations
well below 1 ug/L, but to my surprise, we found oxybenzone concentrations
up to 6 ug/L, which at the time was near the highest I'd seen in the
literature.  Since a few effect concentrations in the literature were less
than 6 ug/L, there was greater risk than I expected.  Since the samples
were collected so close to the surf zone and I expected concentrations
would decline with distance from that zone, we went back out and conducted
sampling designed to test that hypothesis at 2 of the higher-use beaches.
As expected, they did decline with distance from the beach.  Data from
these sampling efforts can be found in Bargar et al (2015), Marine
Pollution Bulletin v101, pp 193-199.  All of those samples were collected
around mid-day when I expect the most swimmers to be present, again under
the presumption that if we found little in the water, then risk was likely
to be minimal.  A few papers have shown diurnal variation of concentrations
(Sankoda et al. 2015, Arch Environ Contam Toxicol v68, pp 217-224,
Tovar-Sanchez et al. 2013, PLOS One v8 issue 8, e65451), presumably in
response to the number of swimmers at the beaches.  I expect the same at
the USVI National Park, but haven't been able to investigate.

The actual concentration to which aquatic organisms are exposed is tough to
determine precisely.  It clearly will vary diurnally making the actual
exposure an average over a span of time that an investigator chooses to
select.  A single discreet sample, while representing an organism's
exposure at that instant, is not representative of its entire exposure.
The organism will integrate exposure over time and location (for mobile
organisms).  We have conducted an experiment in which we tried to mimic, in
a flow-through system, what we'd expect to be the diurnally varying
concentrations at the high-use beaches.  We exposed mosquito-fish (I know,
not a marine organism much less a coral) to this system for 8 weeks,
beginning when the fish were 1-2 days old and then looked at gene
regulation in select tissues.  We also evaluated growth and survival - no
effect there.  We're still evaluating the molecular data.  I'd like to do
the same with coral, but haven't succeeded in securing funding.

I guess my point in saying all of this is that there is a lot of
uncertainty regarding the risk to reefs from the active ingredients in
sunscreens.  The literature base for it is nowhere near that for much of
the other reef-related research.  There is little doubt that the actives
can adversely affect aquatic organisms given adequate exposure.  There is
also little doubt that the spatial extent of potential exposure to the
actives world wide is nowhere near that of the spatial extent of exposure
to elevated temperatures.  Even if concentrations in the water were
sufficient to have an effect, there are only so many beaches or areas where
swimmers are in the water. The sun, however, is just about everywhere.  So
the potential spatial extent of effects is greater for warming than the
sunscreen actives.  However, if a particular chemical is shown to be a
significant risk, resource managers at the local level want and need to do
something about it (I have been told as much by those at the national
park).  Doing so can only alleviate some of the stress.  I think there is
"room" to manage and research both.

On Thu, Feb 7, 2019 at 10:51 AM Douglas Fenner via Coral-List <
coral-list at coral.aoml.noaa.gov<mailto:coral-list at coral.aoml.noaa.gov>> wrote:

I was just made aware of a new paper on some sunscreen UV filter
ingredients, though oxybenzone was not tested.

Fel, J-P, et al 2018.  Photochemical response of the scleractinian
coral *Stylophora
pistillata* to some sunscreen ingredients.  Coral Reefs 38: 109-122.


(become a member of the International Coral Reef Society, and ALL the
articles in Coral Reefs become open-access for you, and you can join
amazingly inexpensively!)

One person pointed out to me that when there is strong evidence that there
is an effective chemical that is less toxic, then more toxic chemicals can
be banned.  Says that happens all the time in the insecticide industry.  I
hope there are effective UV filters that are less toxic and useful for

Another points out that the "conservationists" in the dive industry jump
all over easy things like sunscreens, eager to urge people to take action,
but won't touch global warming with a 10 foot pole (my wording).  That's
treating the scratch while the patient dies of a gunshot wound to the
chest, great way to watch the reefs die under our noses, in my opinion.

If there was direct evidence of coral mortality in the ocean caused by a
sunscreen ingredient, the case for banning it would be stronger.  But where
is the evidence of that???  Bleaching has killed billions of colonies all
over the world, massive coral mortality, obvious to anyone.  But where's
the evidence that sunscreens have caused mass mortality?  As someone
pointed out to me, for virtually every chemical, there is a concentration
at which it becomes toxic.  The real question is, are sunscreen chemicals
toxic to corals at the concentrations at which they occur in the ocean
where corals are?  And it has to be in the water able to affect the coral,
if you put a dispersant in, then chemicals that don't readily dissolve in
the water (and surely the manufacturers don't want it to wash off or
dissolve off of people readily) may then have much higher concentrations
dissolved in the water than would dissolve naturally in the ocean, no
surprise if they are toxic, but that wouldn't be the situation where living
corals are in the ocean.  Does oil dissolve in water?  The amount of oil
floating on the surface isn't what kills corals on the bottom, it is the
small fraction that manages to dissolve in the water that affects the coral
on the bottom (unless the coral is so shallow that the oil or tar balls
cover the coral directly).  Even sunscreen floating on the surface, if it
doesn't dissolve in the water, will have little effect on life in the
surface microlayer, I would think.  A small part dissolves, and the
question is, is that enough to damage corals.  The small part of sunscreen
chemicals floating at the surface which dissolves may not stay in the
surface microlayer but diffuse and be carried by water movement into the
bulk water column, and thus might not be nearly as concentrated at the
surface as the non-dissolving portion.  I haven't tested it, I'm not a
chemist, I defer to those with expertise in this area, please enlighten us.

    There is a sentence in the abstract (which is open access at the URL I
posted above) that says: "It first shows that for many organic filters,
measured concentrations were significantly lower than nominal
concentrations, due to the lipophilic nature of the compounds."  Which
sounds to me like they are saying that the concentration dissolved in the
water was less than calculated based on how much they put into the water,
because it doesn't dissolve readily in water.

    Zinc oxide was found to be toxic to the corals.  Also, another
sentence in the abstract says: "The other UV filters tested showed no
adverse effect on coral symbionts or animal tissue up to the concentration
corresponding to their water solubility limit (and even above)."  I
interpret this to mean that you can dissolve all you can of them in the
water and they don't show an adverse effect on photosynthesis (which is
what was measured).  Note that they didn't test oxybenzone, they tested
other UV filters used in some sunscreens.

Cheers,  Doug

On Tue, Feb 5, 2019 at 9:43 PM Bill Allison <allison.billiam at gmail.com>

I was thinking of sunscreens as one of many insults afflicting the
microlayer ecosystem, and how important that ecosystem is.

On Tue, Feb 5, 2019 at 10:38 PM Douglas Fenner <
douglasfennertassi at gmail.com> wrote:

Good point!  Many or most coral eggs float so they would be in the
surface microlayer, slicks of coral eggs on the surface on the Great
Barrier Reef are large enough you can follow them for a while from
airplanes.  I would guess that sunscreens float, but I don't know.  But
most areas small enough to be contaminated significantly by sunscreens
not very likely to be self-seeding, especially for the majority of
that are broadcast spawners.  Still would be an impact on overall coral
reproduction, though given that the areas that have large numbers of
tourists with sunscreen in the water are minute compared to the world
area, especially in the Indo-Pacific, which of course is most of the
world's reefs, the effect would be pretty small, probably difficult to
measure I would guess.  Maybe higher in an area like the Caribbean where
tourism is large on many islands.
Cheers,  Doug

On Tue, Feb 5, 2019 at 2:05 PM Bill Allison <allison.billiam at gmail.com>

It strikes me that sunscreens will tend to float as will toxins seeping
into the sea from freshwater lenses and fogging pesticides in diesel
carriers, all of which will be harmful to organisms in the surface
Wurl, O. and J. P. Obbard (2004). "A review of pollutants in the
sea-surface microlayer (SML): a unique habitat for marine organisms."
Marine Pollution Bulletin 48(11-12): 1016-1030.
Boundary layers between different environmental compartments represent
critical interfaces for biological, chemical and physical processes.
sea-surface microlayer (uppermost 1-1000 lm layer) forms the boundary
interface between the atmosphere and ocean. Environmental processes are
controlled by the SML, and it is known to play a key role in the global
distribution of anthropogenic pollutants. Due to its unique chemical
composition, the upper organic film of the SML represents both a sink
and a
source for a range of pollutants including chlorinated hydrocarbons,
organotin compounds, petroleum hydrocarbons, polycyclic aromatic
hydrocarbons (PAH) and heavy metals. These pollutants can be enriched
the SML by up to 500 times relative to concentrations occurring in the
underlying bulk water column. The SML is also a unique ecosystem,
as an important habitat for fish eggs and larvae. Concentration ranges
enrichment factors of pollutants in the SML in different areas of the
world's oceans have been critically reviewed, together with available
toxicity data for marine biota found within the SML. Overall, the SML
highly contaminated in many urban and industrialized areas of the
resulting in severe ecotoxicological impacts. Such impacts may lead to
drastic effects on the marine food web and to fishery recruitment in
coastal waters. Studies of the toxicity of fish eggs and larvae
exposed to
the SML contaminants have shown that the SML in polluted areas leads to
significantly higher rates of mortality and abnormality of fish
embryos and

Douglas Fenner
Ocean Associates, Inc. Contractor
NOAA Fisheries Service
Pacific Islands Regional Office
PO Box 7390
Pago Pago, American Samoa 96799  USA

How to win public support for a global carbon tax


Global warming will happen faster than we think.


Nations falling short of emissions cuts set by Paris climate pact, analysis

Coral-List mailing list
Coral-List at coral.aoml.noaa.gov

Tim Bargar, Ph.D.
Research Ecotoxicologist
The USGS Wetland and Aquatic Research Center
7920 NW 71st Street
Gainesville, Florida 32653
T - (352) 264-3520
F - (352) 378-4956

"Do not withhold good from those who deserve it when it's in your power to
help them."
Coral-List mailing list
Coral-List at coral.aoml.noaa.gov<mailto:Coral-List at coral.aoml.noaa.gov>

More information about the Coral-List mailing list